HP StorageWorks 1000 HP StorageWorks 1000 Modular Smart Array reference guide - Page 20

Array Accelerator Features:, bit Error Checking and Correcting ECC SDRAM memory

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MSA1000 Hardware Components The read-ahead cache detects sequential accesses to the array, reads ahead data, and stores the data in the cache until the next read access arrives. If the data is of a sequential nature, the data can be loaded immediately into memory, avoiding the latency of a disk access. If the MSA1000 Controller fails before cached data is stored on the disk, the Array Accelerator and its integrated batteries may be removed from one MSA1000 Controller and installed on a replacement controller. Any data in the Array Accelerator that has not been written to the hard drive will be transferred to the replacement MSA1000 Controller. Array Accelerator Features: Other features of the Array Accelerator: ■ Mounted on a removable daughterboard (allows stored data to be moved to another controller if the original controller fails) ■ Backed up with replaceable batteries ■ Upgradable to 512 MB (256 MB per controller) ■ Adjustable read/write ratio - usually set during array configuration but can be changed at any time ■ 16-bit Error Checking and Correcting (ECC) SDRAM memory ECC detects and corrects all single-bit memory errors. It also detects all two-bit memory errors in any position, and most three- and four-bit memory errors in a single SDRAM. With ECC, an entire memory chip can also fail without data loss. This provides a high level of data integrity by ensuring the correction of common memory errors without affecting performance. Array Accelerator Batteries The Array Accelerator has two rechargeable and replaceable Nickel Metal Hydride (NiMH) battery packs. Under normal operating conditions, these should last for three years before replacement is necessary. They are continuously recharged via a "trickle" charging process whenever the MSA1000 storage system is powered on. The battery packs protect data on the Array Accelerator against equipment failure or power outage for up to four continuous days. Note: Temperature, age, and cache size may affect battery life. 20 HP StorageWorks 1000 Modular Smart Array Reference Guide

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MSA1000 Hardware Components
20
HP StorageWorks 1000 Modular Smart Array Reference Guide
The read-ahead cache detects sequential accesses to the array, reads ahead data,
and stores the data in the cache until the next read access arrives. If the data is of a
sequential nature, the data can be loaded immediately into memory, avoiding the
latency of a disk access.
If the MSA1000 Controller
fails before cached data is stored on the disk, the
Array Accelerator and its integrated batteries may be removed from one
MSA1000 Controller
and installed on a replacement controller. Any data in the
Array Accelerator that has not been written to the hard drive will be transferred to
the replacement MSA1000 Controller.
Array Accelerator Features:
Other features of the Array Accelerator:
■
Mounted on a removable daughterboard (allows stored data to be moved to
another controller if the original controller fails)
■
Backed up with replaceable batteries
■
Upgradable to 512 MB (256 MB per controller)
■
Adjustable read/write ratio - usually set during array configuration but can be
changed at any time
■
16-bit Error Checking and Correcting (ECC) SDRAM memory
ECC detects and corrects all single-bit memory errors. It also detects all
two-bit memory errors in any position, and most three- and four-bit memory
errors in a single SDRAM. With ECC, an entire memory chip can also fail
without data loss. This provides a high level of data integrity by ensuring the
correction of common memory errors without affecting performance.
Array Accelerator Batteries
The Array Accelerator has two rechargeable and replaceable Nickel Metal
Hydride (NiMH) battery packs. Under normal operating conditions, these should
last for three years before replacement is necessary. They are continuously
recharged via a “trickle” charging process whenever the MSA1000 storage system
is powered on.
The battery packs protect data on the Array Accelerator against equipment failure
or power outage for up to four continuous days.
Note:
Temperature, age, and cache size may affect battery life.